The present invention relates to a propeller assembly, and more specifically to an apparatus and method for deploying a propeller assembly, a which is diametrically larger than an aerial projectile's diameter, from a folded configuration to a deployed configuration during the fight of the aerial projectile.
Some projectiles, which require a propeller assembly, are fired from a gun or some other launching system that has a constricted launch area. These projectiles may have a propeller assembly that is diametrically larger than the projectile's diameter. The gun or other launching system may have a constricted launch area that may only contain the projectile body but not the diametrically larger propeller assembly.
One option for fitting both a projectile and its propeller assembly inside a limited launch area is to package the propeller assembly so that the propeller blades are not diametrically larger than the projectile prior to launch. For example, it is believed that U.S. Pat. No. 4,986,185 discloses dual blade propellers made of flexible metal or fabric loops or strips. The propeller blades are folded in a closely packed, nesting arrangement. However, this prior art is designed to deploy the propeller blades as soon as the projectile is free of the restricted launch area. Furthermore, the blades are loops, thus each blade has a limited surface area.
Propeller blades hinged to a hub are also known in the prior art. For example, it is believed that U.S. Pat. No. 4,204,806 discloses a foldable marine propeller assembly that is attached to a drive shaft. Though the folded propeller assembly appears to have an aerodynamically efficient configuration, once employed, the area once occupied by the propeller blades is now a flat, blunt area that is no longer as aerodynamically efficient.
Accordingly, it would be advantageous to provide an apparatus and method that is simple and robust enough to deploy solid propellers other than immediately after launch where the propeller blades are capable of withstanding the environment experienced in launching the projectile. It would also be advantageous for the propeller assembly to maintain an aerodynamically efficient configuration after the deployment of the propeller blades.